代码实现：

/**
 * Note: The returned array must be malloced, assume caller calls free().
 */
int* productExceptSelf(int *nums, int numsSize, int *returnSize) {
    // 左乘积
    int l[numsSize];
    l[0] = 1;
    for (int i = 1; i < numsSize; i++) {
        l[i] = l[i - 1] * nums[i - 1];
    }
    // 右乘积
    int r[numsSize];
    r[numsSize - 1] = 1;
    for (int i = numsSize - 2; i >= 0; i--) {
        r[i] = r[i + 1] * nums[i + 1];
    }
    int *answer = malloc(sizeof(int) * numsSize);
    *returnSize = numsSize;
    for (int i = 0; i < numsSize; i++) {
        answer[i] = l[i] * r[i]; // 左 * 右
    }
    return answer;
}